diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..2287363
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,4 @@
+badblocks: badblocks.o
+	gcc -o badblocks -g3 -Wall badblocks.c
+clean:
+	rm -f badblocks badblocks.o
diff --git a/badblocks.c b/badblocks.c
new file mode 100644
index 0000000..ca52647
--- /dev/null
+++ b/badblocks.c
@@ -0,0 +1,2225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Bad block management
+ *
+ * - Heavily based on MD badblocks code from Neil Brown
+ *
+ * Copyright (c) 2015, Intel Corporation.
+ *
+ * Improvement for handling multiple ranges by Coly Li <colyli@suse.de>
+ */
+
+#define _GNU_SOURCE             /* See feature_test_macros(7) */
+#include <stdlib.h>
+#include <linux/types.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <limits.h>
+#include <assert.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+
+
+#define PAGE_SIZE       4096
+typedef unsigned long long sector_t;
+typedef unsigned long long u64;
+typedef _Bool bool;
+
+#define BB_LEN_MASK     (0x00000000000001FFULL)
+#define BB_OFFSET_MASK  (0x7FFFFFFFFFFFFE00ULL)
+#define BB_ACK_MASK     (0x8000000000000000ULL)
+#define BB_MAX_LEN      512
+#define BB_OFFSET(x)    (((x) & BB_OFFSET_MASK) >> 9)
+#define BB_LEN(x)       (((x) & BB_LEN_MASK) + 1)
+#define BB_END(x)       (BB_OFFSET(x) + BB_LEN(x))
+#define BB_ACK(x)       (!!((x) & BB_ACK_MASK))
+#define BB_MAKE(a, l, ack) (((a)<<9) | ((l)-1) | ((u64)(!!(ack)) << 63))
+
+/* Bad block numbers are stored in a single page.
+ * 64bits is used for each block or extent.
+ * 54 bits are sector number, 9 bits are extent size,
+ * 1 bit is an 'acknowledged' flag.
+ */
+#define MAX_BADBLOCKS   (PAGE_SIZE/8)
+#define GFP_KERNEL      0
+#define true    1
+#define false   0
+
+#define WARN_ON(condition) ({ \
+		if (!!(condition)) \
+			printf("warning on %s:%d\n", __func__, __LINE__); \
+})
+
+#define BUG() ({printf("BUG on %s:%d\n", __func__, __LINE__); exit(1); })
+
+struct device {
+	int val;
+};
+
+struct badblocks {
+	struct device *dev;
+	int count;              /* count of bad blocks */
+	int unacked_exist;      /* there probably are unacknowledged
+				 * bad blocks.  This is only cleared
+				 * when a read discovers none
+				 */
+	int shift;		/* shift from sectors to block size
+				 * a -ve shift means badblocks are
+				 * disabled.*/
+	u64 *page;		/* badblock list */
+	int changed;
+	unsigned long lock;
+	sector_t sector;
+	sector_t size;		/* in sectors */
+};
+
+struct badblocks_context {
+	sector_t start;
+	sector_t len;
+	sector_t orig_start;
+	sector_t orig_len;
+	int ack;
+	int first_prev;
+};
+
+int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
+		     sector_t *first_bad, int *bad_sectors);
+int badblocks_set(struct badblocks *bb, sector_t s, int sectors,
+		   int acknowledged);
+int badblocks_clear(struct badblocks *bb, sector_t s, int sectors);
+void ack_all_badblocks(struct badblocks *bb);
+ssize_t badblocks_show(struct badblocks *bb, int unack);
+ssize_t badblocks_store(struct badblocks *bb, const char *page, size_t len,
+			 int unack);
+int badblocks_init(struct badblocks *bb, int enable);
+void badblocks_exit(struct badblocks *bb);
+
+static inline void *kzalloc(int size, int flag)
+{
+	void *p = malloc(size);
+	memset(p, 0, size);
+	return p;
+}
+
+static inline void kfree(void *page)
+{
+	free(page);
+}
+
+#define roundup(x, y) (			\
+{						\
+	typeof(y) __y = y;			\
+	(((x) + (__y - 1)) / __y) * __y;	\
+}						\
+)
+
+#define rounddown(x, y) (			\
+{						\
+	typeof(x) __x = (x);			\
+	__x - (__x % (y));			\
+}						\
+)
+
+#define fallthrough     do { } while (0)
+
+/**
+ * min - return minimum of two values of the same or compatible types
+ * @x: first value
+ * @y: second value
+ */
+#define min(x, y)        ((x) < (y) ? (x) : (y))
+#define min_t(t, x, y) ((x) < (y) ? (x) : (y))
+
+#define write_seqlock_irqsave(_lock, _flags)	((_flags) = *(_lock))
+#define write_sequnlock_irqrestore(_lock, _flags) ((*(_lock)) = (_flags))
+#define write_seqlock_irq(lock) do { } while (0)
+#define write_sequnlock_irq(lock) do { } while (0)
+#define read_seqbegin(lock) 1
+#define read_seqretry(lock, seq)  (!!((seq) && 0))
+#define seqlock_init(lock) do { } while (0)
+#define EXPORT_SYMBOL_GPL(sym)
+
+static void *devm_kzalloc(struct device *dev, int size, int flags)
+{
+	void *buf = malloc(size);
+	if (buf)
+		memset(buf, 0, size);
+	return buf;
+}
+
+static void devm_kfree(struct device *dev, void *mem)
+{
+	free(mem);
+}
+
+static inline int badblocks_full(struct badblocks *bb)
+{
+	return (bb->count >= MAX_BADBLOCKS);
+}
+
+static inline int badblocks_empty(struct badblocks *bb)
+{
+	return (bb->count == 0);
+}
+
+static inline void set_changed(struct badblocks *bb)
+{
+	if (bb->changed != 1)
+		bb->changed = 1;
+}
+
+/*
+ * The purpose of badblocks set/clear is to manage bad blocks ranges which are
+ * identified by LBA addresses.
+ *
+ * When the caller of badblocks_set() wants to set a range of bad blocks, the
+ * setting range can be acked or unacked. And the setting range may merge,
+ * overwrite, skip the overlaypped already set range, depends on who they are
+ * overlapped or adjacent, and the acknowledgment type of the ranges. It can be
+ * more complicated when the setting range covers multiple already set bad block
+ * ranges, with restritctions of maximum length of each bad range and the bad
+ * table space limitation.
+ *
+ * It is difficut and unnecessary to take care of all the possible situations,
+ * for setting a large range of bad blocks, we can handle it by dividing the
+ * large range into smaller ones when encounter overlap, max range length or
+ * bad table full conditions. Every time only a smaller piece of the bad range
+ * is handled with a limited number of conditions how it is interacted with
+ * possible overlapped or adjacent already set bad block ranges. Then the hard
+ * complicated problem can be much simpler to habndle in proper way.
+ *
+ * When setting a range of bad blocks to the bad table, the simplified situations
+ * to be considered are, (The already set bad blocks ranges are naming with
+ *  prefix E, and the setting bad blocks range is naming with prefix S)
+ *
+ * 1) A setting range is not overlapped or adjacent to any other already set bad
+ *    block range.
+ *                         +--------+
+ *                         |    S   |
+ *                         +--------+
+ *        +-------------+               +-------------+
+ *        |      E1     |               |      E2     |
+ *        +-------------+               +-------------+
+ *    For this situation if the bad blocks table is not full, just allocate a
+ *    free slot from the bad blocks table to mark the setting range S. The
+ *    result is,
+ *        +-------------+  +--------+   +-------------+
+ *        |      E1     |  |    S   |   |      E2     |
+ *        +-------------+  +--------+   +-------------+
+ * 2) A setting range starts exactly at a start LBA of an already set bad blocks
+ *    range.
+ * 2.1) The setting range size < already set range size
+ *        +--------+
+ *        |    S   |
+ *        +--------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 2.1.1) If S and E are both acked or unacked range, the setting range S can
+ *    be merged into existing bad range E. The result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 2.1.2) If S is uncked setting and E is acked, the setting will be dinied, and
+ *    the result is,
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 2.1.3) If S is acked setting and E is unacked, range S can overwirte on E.
+ *    An extra slot from the bad blocks table will be allocated for S, and head
+ *    of E will move to end of the inserted range E. The result is,
+ *        +--------+----+
+ *        |    S   | E  |
+ *        +--------+----+
+ * 2.2) The setting range size == already set range size
+ * 2.2.1) If S and E are both acked or unacked range, the setting range S can
+ *    be merged into existing bad range E. The result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 2.2.2) If S is uncked setting and E is acked, the setting will be dinied, and
+ *    the result is,
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 2.2.3) If S is acked setting and E is unacked, range S can overwirte all of
+      bad blocks range E. The result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 2.3) The setting range size > already set range size
+ *        +-------------------+
+ *        |          S        |
+ *        +-------------------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ *    For such situation, the setting range S can be treated as two parts, the
+ *    first part (S1) is as same size as the already set range E, the second
+ *    part (S2) is the rest of setting range.
+ *        +-------------+-----+        +-------------+       +-----+
+ *        |    S1       | S2  |        |     S1      |       | S2  |
+ *        +-------------+-----+  ===>  +-------------+       +-----+
+ *        +-------------+              +-------------+
+ *        |      E      |              |      E      |
+ *        +-------------+              +-------------+
+ *    Now we only focus on how to handle the setting range S1 and already set
+ *    range E, which are already explained in 1.2), for the rest S2 it will be
+ *    handled later in next loop.
+ * 3) A setting range starts before the start LBA of an already set bad blocks
+ *    range.
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ *             +-------------+
+ *             |      E      |
+ *             +-------------+
+ *    For this situation, the setting range S can be divided into two parts, the
+ *    first (S1) ends at the start LBA of already set range E, the second part
+ *    (S2) starts exactly at a start LBA of the already set range E.
+ *        +----+---------+             +----+      +---------+
+ *        | S1 |    S2   |             | S1 |      |    S2   |
+ *        +----+---------+      ===>   +----+      +---------+
+ *             +-------------+                     +-------------+
+ *             |      E      |                     |      E      |
+ *             +-------------+                     +-------------+
+ *    Now only the first part S1 should be handled in this loop, which is in
+ *    similar condition as 1). The rest part S2 has exact same start LBA address
+ *    of the already set range E, they will be handled in next loop in one of
+ *    situations in 2).
+ * 4) A setting range starts after the start LBA of an already set bad blocks
+ *    range.
+ * 4.1) If the setting range S exactly matches the tail part of already set bad
+ *    blocks range E, like the following chart shows,
+ *            +---------+
+ *            |   S     |
+ *            +---------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 4.1.1) If range S and E have same ackknowledg value (both acked or unacked),
+ *    they will be merged into one, the result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 4.1.2) If range E is acked and the setting range S is unacked, the setting
+ *    request of S will be rejected, the result is,
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 4.1.3) If range E is unacked, and the setting range S is acked, then S may
+ *    overwrite the overlapped range of E, the result is,
+ *        +---+---------+
+ *        | E |    S    |
+ *        +---+---------+
+ * 4.2) If the setting range S stays in middle of an already set range E, like
+ *    the following chart shows,
+ *             +----+
+ *             | S  |
+ *             +----+
+ *        +--------------+
+ *        |       E      |
+ *        +--------------+
+ * 4.2.1) If range S and E have same ackknowledg value (both acked or unacked),
+ *    they will be merged into one, the result is,
+ *        +--------------+
+ *        |       S      |
+ *        +--------------+
+ * 4.2.2) If range E is acked and the setting range S is unacked, the setting
+ *    request of S will be rejected, the result is also,
+ *        +--------------+
+ *        |       E      |
+ *        +--------------+
+ * 4.2.3) If range E is unacked, and the setting range S is acked, then S will
+ *    inserted into middle of E and split previous range E into twp parts (E1
+ *    and E2), the result is,
+ *        +----+----+----+
+ *        | E1 |  S | E2 |
+ *        +----+----+----+
+ * 4.3) If the setting bad blocks range S is overlapped with an already set bad
+ *    blocks range E. The range S starts after the start LBA of range E, and
+ *    ends after the end LBA of range E, as the following chart shows,
+ *            +-------------------+
+ *            |          S        |
+ *            +-------------------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ *    For this situation the range S can be divided into two parts, the first
+ *    part (S1) ends at end range E, and the second part (S2) has rest range of
+ *    origin S.
+ *            +---------+---------+            +---------+      +---------+
+ *            |    S1   |    S2   |            |    S1   |      |    S2   |
+ *            +---------+---------+  ===>      +---------+      +---------+
+ *        +-------------+                  +-------------+
+ *        |      E      |                  |      E      |
+ *        +-------------+                  +-------------+
+ *     Now in this loop the setting range S1 and already set range E can be
+ *     handled as the situations 4), the rest range S2 will be handled in next
+ *     loop and ignored in this loop.
+ * 5) A setting bad blocks range S is adjacent to one or more already set bad
+ *    blocks range(s), and they are all acked or unacked range.
+ * 5.1) Front merge: If the already set bad blocks range E is before setting
+ *    range S and they are adjacent,
+ *                +------+
+ *                |  S   |
+ *                +------+
+ *        +-------+
+ *        |   E   |
+ *        +-------+
+ * 5.1.1) When total size of range S and E <= BB_MAX_LEN, and their acknowledge
+ *    values are same, the setting range S can front merges into range E. The
+ *    result is,
+ *        +--------------+
+ *        |       S      |
+ *        +--------------+
+ * 5.1.2) Otherwise these two ranges cannot merge, just insert the setting
+ *    range S right after already set range E into the bad blocks table. The
+ *    result is,
+ *        +--------+------+
+ *        |   E    |   S  |
+ *        +--------+------+
+ * 6) Special cases which above conditions cannot handle
+ * 6.1) Multiple already set ranges may merge into less ones in a full bad table
+ *        +-------------------------------------------------------+
+ *        |                           S                           |
+ *        +-------------------------------------------------------+
+ *        |<----- BB_MAX_LEN ----->|
+ *                                 +-----+     +-----+   +-----+
+ *                                 | E1  |     | E2  |   | E3  |
+ *                                 +-----+     +-----+   +-----+
+ *     In the above example, when the bad blocks table is full, inserting the
+ *     first part of setting range S will fail because no more available slot
+ *     can be allocated from bad blocks table. In this situation a proper
+ *     setting method should be go though all the setting bad blocks range and
+ *     look for chance to merge already set ranges into less ones. When there
+ *     is available slot from bad blocks table, re-try again to handle more
+ *     setting bad blocks ranges as many as possible.
+ *        +------------------------+
+ *        |          S3            |
+ *        +------------------------+
+ *        |<----- BB_MAX_LEN ----->|
+ *                                 +-----+-----+-----+---+-----+--+
+ *                                 |       S1        |     S2     |
+ *                                 +-----+-----+-----+---+-----+--+
+ *     The above chart shows although the first part (S3) cannot be inserted due
+ *     to no-space in bad blocks table, but the following E1, E2 and E3 ranges
+ *     can be merged with rest part of S into less range S1 and S2. Now there is
+ *     1 free slot in bad blocks table.
+ *        +------------------------+-----+-----+-----+---+-----+--+
+ *        |           S3           |       S1        |     S2     |
+ *        +------------------------+-----+-----+-----+---+-----+--+
+ *     Since the bad blocks table is not full anymore, re-try again for the
+ *     origin setting range S. Now the setting range S3 can be inserted into the
+ *     bad blocks table with previous freed slot from multiple ranges merge.
+ * 6.2) Front merge after overwrite
+ *    In the following example, in bad blocks table, E1 is an acked bad blocks
+ *    range and E2 is an unacked bad blocks range, therefore they are not able
+ *    to merge into a larger range. The setting bad blocks range S is acked,
+ *    therefore part of E2 can be overwritten by S.
+ *                      +--------+
+ *                      |    S   |                             acknowledged
+ *                      +--------+                         S:       1
+ *              +-------+-------------+                   E1:       1
+ *              |   E1  |    E2       |                   E2:       0
+ *              +-------+-------------+
+ *     With previosu simplified routines, after overwiting part of E2 with S,
+ *     the bad blocks table should be (E3 is remaining part of E2 which is not
+ *     overwritten by S),
+ *                                                             acknowledged
+ *              +-------+--------+----+                    S:       1
+ *              |   E1  |    S   | E3 |                   E1:       1
+ *              +-------+--------+----+                   E3:       0
+ *     The above result is correct but not perfect. Range E1 and S in the bad
+ *     blocks table are all acked, merging them into a larger one range may
+ *     occupy less bad blocks table space and make badblocks_check() faster.
+ *     Therefore in such situation, after overwiting range S, the previous range
+ *     E1 should be checked for possible front combination. Then the ideal
+ *     result can be,
+ *              +----------------+----+                        acknowledged
+ *              |       E1       | E3 |                   E1:       1
+ *              +----------------+----+                   E3:       0
+ * 6.3) Behind merge: If the already set bad blocks range E is behind the setting
+ *    range S and they are adjacent. Normally we don't need to care about this
+ *    because front merge handles this while going though range S from head to
+ *    tail, except for the tail part of range S. When the setting range S are
+ *    fully handled, all the above simplified routine doesn't check whether the
+ *    tail LBA of range S is adjacent to the next already set range and not able
+ *    to them if they are mergeable.
+ *        +------+
+ *        |  S   |
+ *        +------+
+ *               +-------+
+ *               |   E   |
+ *               +-------+
+ *    For the above special stiuation, when the setting range S are all handled
+ *    and the loop ends, an extra check is necessary for whether next already
+ *    set range E is right after S and mergeable.
+ * 6.2.1) When total size of range E and S <= BB_MAX_LEN, and their acknowledge
+ *    values are same, the setting range S can behind merges into range E. The
+ *    result is,
+ *        +--------------+
+ *        |       S      |
+ *        +--------------+
+ * 6.2.2) Otherwise these two ranges cannot merge, just insert the setting range
+ *     S infront of the already set range E in the bad blocks table. The result
+ *     is,
+ *        +------+-------+
+ *        |  S   |   E   |
+ *        +------+-------+
+ *
+ * All the above 5 simplified situations and 3 special cases may cover 99%+ of
+ * the bad block range setting conditions. Maybe there is some rare corner case
+ * is not considered and optimized, it won't hurt if badblocks_set() fails due
+ * to no space, or some ranges are not merged to save bad blocks table space.
+ *
+ * Inside badblocks_set() each loop starts by jumping to re_insert label, every
+ * time for the new loop prev_badblocks() is called to find an already set range
+ * which starts before or at current setting range. Since the setting bad blocks
+ * range is handled from head to tail, most of the cases it is unnecessary to do
+ * the binary search inside prev_badblocks(), it is possible to provide a hint
+ * to prev_badblocks() for a fast path, then the expensive binary search can be
+ * avoided. In my test with the hint to prev_badblocks(), except for the first
+ * loop, all rested calls to prev_badblocks() can go into the fast path and
+ * return correct bad blocks table index immediately.
+ *
+ *
+ * Clearing a bad blocks range from the bad block table has similar idea as
+ * setting does, but much more simpler. The only thing needs to be noticed is
+ * when the clearning range hits middle of a bad block range, the existing bad
+ * block range will split into two, and one more item should be added into the
+ * bad block table. The simplified situations to beconsidered are, (The already
+ * set bad blocks ranges in bad block table are naming with prefix E, and the
+ * clearing bad blocks range is naming with prefix C)
+ *
+ * 1) A clearing range is not overlapped to any already set ranges in bad block
+ *    table.
+ *    +-----+         |          +-----+         |          +-----+
+ *    |  C  |         |          |  C  |         |          |  C  |
+ *    +-----+         or         +-----+         or         +-----+
+ *            +---+   |   +----+         +----+  |  +---+
+ *            | E |   |   | E1 |         | E2 |  |  | E |
+ *            +---+   |   +----+         +----+  |  +---+
+ *    For the above situations, no bad block to be cleared and no failure
+ *    happens, simply returns 0.
+ * 2) The clearing range hits middle of an already setting bad blocks range in
+ *    the bad block table.
+ *            +---+
+ *            | C |
+ *            +---+
+ *     +-----------------+
+ *     |         E       |
+ *     +-----------------+
+ *    In this situation if the bad block table is not full, the range E will be
+ *    split into two ranges E1 and E2. The result is,
+ *     +------+   +------+
+ *     |  E1  |   |  E2  |
+ *     +------+   +------+
+ * 3) The clearing range starts exactly at same LBA as an already set bad block range
+ *    from the bad block table.
+ * 3.1) Partially covered at head part
+ *         +------------+
+ *         |     C      |
+ *         +------------+
+ *         +-----------------+
+ *         |         E       |
+ *         +-----------------+
+ *    For this situation, the overlapped already set range will update the
+ *    start LBA to end of C and shrink the range to BB_LEN(E) - BB_LEN(C). No
+ *    item deleted from bad block table. The result is,
+ *                      +----+
+ *                      | E1 |
+ *                      +----+
+ * 3.2) Exact fully covered
+ *         +-----------------+
+ *         |         C       |
+ *         +-----------------+
+ *         +-----------------+
+ *         |         E       |
+ *         +-----------------+
+ *    For this situation the whole bad blocks range E will be cleared and its
+ *    corresponded item is deleted from the bad block table.
+ * 4) The clearing range exactly ends at same LBA as an already set bad block
+ *    range.
+ *                   +-------+
+ *                   |   C   |
+ *                   +-------+
+ *         +-----------------+
+ *         |         E       |
+ *         +-----------------+
+ *    For the above situation, the already set range E is updated to shrink its
+ *    end to the start of C, and reduce its length to BB_LEN(E) - BB_LEN(C).
+ *    The result is,
+ *         +---------+
+ *         |    E    |
+ *         +---------+
+ * 5) The clearing range is partially overlapped with an already set bad block
+ *    range from the bad block table.
+ * 5.1) The already set bad block range is front overlapped with the clearing
+ *    range.
+ *         +----------+
+ *         |     C    |
+ *         +----------+
+ *              +------------+
+ *              |      E     |
+ *              +------------+
+ *   For such situation, the clearing range C can be treated as two parts. The
+ *   first part ends at the start LBA of range E, and the second part starts at
+ *   same LBA of range E.
+ *         +----+-----+               +----+   +-----+
+ *         | C1 | C2  |               | C1 |   | C2  |
+ *         +----+-----+         ===>  +----+   +-----+
+ *              +------------+                 +------------+
+ *              |      E     |                 |      E     |
+ *              +------------+                 +------------+
+ *   Now the first part C1 can be handled as condition 1), and the second part C2 can be
+ *   handled as condition 3.1) in next loop.
+ * 5.2) The already set bad block range is behind overlaopped with the clearing
+ *   range.
+ *                 +----------+
+ *                 |     C    |
+ *                 +----------+
+ *         +------------+
+ *         |      E     |
+ *         +------------+
+ *   For such situation, the clearing range C can be treated as two parts. The
+ *   first part C1 ends at same end LBA of range E, and the second part starts
+ *   at end LBA of range E.
+ *                 +----+-----+                 +----+    +-----+
+ *                 | C1 | C2  |                 | C1 |    | C2  |
+ *                 +----+-----+  ===>           +----+    +-----+
+ *         +------------+               +------------+
+ *         |      E     |               |      E     |
+ *         +------------+               +------------+
+ *   Now the first part clearing range C1 can be handled as condition 4), and
+ *   the second part clearing range C2 can be handled as condition 1) in next
+ *   loop.
+ *
+ *   All bad blocks range clearing can be simplified into the above 5 situations
+ *   by only handling the head part of the clearing range in each run of the
+ *   while-loop. The idea is similar to bad blocks range setting but much
+ *   simpler.
+ */
+
+/*
+ * Find the range starts at-or-before 's' from bad table. The search
+ * starts from index 'hint' and stops at index 'hint_end' from the bad
+ * table.
+ */
+static int prev_by_hint(struct badblocks *bb, sector_t s, int hint)
+{
+	u64 *p = bb->page;
+	int ret = -1;
+	int hint_end = hint + 2;
+
+	while ((hint < hint_end) && ((hint + 1) <= bb->count) &&
+	       (BB_OFFSET(p[hint]) <= s)) {
+		if ((hint + 1) == bb->count || BB_OFFSET(p[hint + 1]) > s) {
+			ret = hint;
+			break;
+		}
+		hint++;
+	}
+
+	return ret;
+}
+
+/*
+ * Find the range starts at-or-before bad->start. If 'hint' is provided
+ * (hint >= 0) then search in the bad table from hint firstly. It is
+ * very probably the wanted bad range can be found from the hint index,
+ * then the unnecessary while-loop iteration can be avoided.
+ */
+static int prev_badblocks(struct badblocks *bb, struct badblocks_context *bad,
+			  int hint)
+{
+	u64 *p;
+	int lo, hi;
+	sector_t s = bad->start;
+	int ret = -1;
+
+	if (!bb->count)
+		goto out;
+
+	if (hint >= 0) {
+		ret = prev_by_hint(bb, s, hint);
+		if (ret >= 0)
+			goto out;
+	}
+
+	lo = 0;
+	hi = bb->count;
+	p = bb->page;
+
+	while (hi - lo > 1) {
+		int mid = (lo + hi)/2;
+		sector_t a = BB_OFFSET(p[mid]);
+
+		if (a <= s)
+			lo = mid;
+		else
+			hi = mid;
+	}
+
+	if (BB_OFFSET(p[lo]) <= s)
+		ret = lo;
+out:
+	return ret;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' can be backward merged
+ * with the bad range (from the bad table) index by 'behind'.
+ */
+static bool can_merge_behind(struct badblocks *bb, struct badblocks_context *bad,
+			     int behind)
+{
+	u64 *p = bb->page;
+	sector_t s = bad->start;
+	sector_t sectors = bad->len;
+	int ack = bad->ack;
+
+	if ((s <= BB_OFFSET(p[behind])) &&
+	    ((s + sectors) >= BB_OFFSET(p[behind])) &&
+	    ((BB_END(p[behind]) - s) <= BB_MAX_LEN) &&
+	    BB_ACK(p[behind]) == ack)
+		return true;
+	return false;
+}
+
+/*
+ * Do backward merge for range indicated by 'bad' and the bad range
+ * (from the bad table) indexed by 'behind'. The return value is merged
+ * sectors from bad->len.
+ */
+static int behind_merge(struct badblocks *bb, struct badblocks_context *bad,
+			int behind)
+{
+	u64 *p = bb->page;
+	sector_t s = bad->start;
+	sector_t sectors = bad->len;
+	int ack = bad->ack;
+	int merged = 0;
+
+	WARN_ON(s > BB_OFFSET(p[behind]));
+	WARN_ON((s + sectors) < BB_OFFSET(p[behind]));
+
+	if (s < BB_OFFSET(p[behind])) {
+		WARN_ON((BB_LEN(p[behind]) + merged) >= BB_MAX_LEN);
+
+		merged = min_t(sector_t, sectors, BB_OFFSET(p[behind]) - s);
+		p[behind] =  BB_MAKE(s, BB_LEN(p[behind]) + merged, ack);
+	} else {
+		merged = min_t(sector_t, sectors, BB_LEN(p[behind]));
+	}
+
+	WARN_ON(merged == 0);
+
+	return merged;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' can be forward
+ * merged with the bad range (from the bad table) indexed by 'prev'.
+ */
+static bool can_merge_front(struct badblocks *bb, int prev,
+			    struct badblocks_context *bad)
+{
+	u64 *p = bb->page;
+	sector_t s = bad->start;
+	int ack = bad->ack;
+
+	if (BB_ACK(p[prev]) == ack &&
+	    (s < BB_END(p[prev]) ||
+	     (s == BB_END(p[prev]) && (BB_LEN(p[prev]) < BB_MAX_LEN))))
+		return true;
+	return false;
+}
+
+/*
+ * Do forward merge for range indicated by 'bad' and the bad range
+ * (from bad table) indexed by 'prev'. The return value is sectors
+ * merged from bad->len.
+ */
+static int front_merge(struct badblocks *bb, int prev, struct badblocks_context *bad)
+{
+	sector_t sectors = bad->len;
+	sector_t s = bad->start;
+	int ack = bad->ack;
+	u64 *p = bb->page;
+	int merged = 0;
+
+	WARN_ON(s > BB_END(p[prev]));
+
+	if (s < BB_END(p[prev])) {
+		merged = min_t(sector_t, sectors, BB_END(p[prev]) - s);
+	} else {
+		merged = min_t(sector_t, sectors, BB_MAX_LEN - BB_LEN(p[prev]));
+		if ((prev + 1) < bb->count &&
+		    merged > (BB_OFFSET(p[prev + 1]) - BB_END(p[prev]))) {
+			merged = BB_OFFSET(p[prev + 1]) - BB_END(p[prev]);
+		}
+
+		p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+				  BB_LEN(p[prev]) + merged, ack);
+	}
+
+	return merged;
+}
+
+/*
+ * 'Combine' is a special case which can_merge_front() is not able to
+ * handle: If a bad range (indexed by 'prev' from bad table) exactly
+ * starts as bad->start, and the bad range ahead of 'prev' (indexed by
+ * 'prev - 1' from bad table) exactly ends at where 'prev' starts, and
+ * the sum of their lengths does not exceed BB_MAX_LEN limitation, then
+ * these two bad range (from bad table) can be combined.
+ *
+ * Return 'true' if bad ranges indexed by 'prev' and 'prev - 1' from bad
+ * table can be combined.
+ */
+static bool can_combine_front(struct badblocks *bb, int prev,
+			      struct badblocks_context *bad)
+{
+	u64 *p = bb->page;
+
+	if ((prev > 0) &&
+	    (BB_OFFSET(p[prev]) == bad->start) &&
+	    (BB_END(p[prev - 1]) == BB_OFFSET(p[prev])) &&
+	    (BB_LEN(p[prev - 1]) + BB_LEN(p[prev]) <= BB_MAX_LEN) &&
+	    (BB_ACK(p[prev - 1]) == BB_ACK(p[prev])))
+		return true;
+	return false;
+}
+
+/*
+ * Combine the bad ranges indexed by 'prev' and 'prev - 1' (from bad
+ * table) into one larger bad range, and the new range is indexed by
+ * 'prev - 1'.
+ */
+static void front_combine(struct badblocks *bb, int prev)
+{
+	u64 *p = bb->page;
+
+	p[prev - 1] = BB_MAKE(BB_OFFSET(p[prev - 1]),
+			      BB_LEN(p[prev - 1]) + BB_LEN(p[prev]),
+			      BB_ACK(p[prev]));
+	if ((prev + 1) < bb->count)
+		memmove(p + prev, p + prev + 1, (bb->count - prev - 1) * 8);
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' is exactly forward
+ * overlapped with the bad range (from bad table) indexed by 'front'.
+ * Exactly forward overlap means the bad range (from bad table) indexed
+ * by 'prev' does not cover the whole range indicated by 'bad'.
+ */
+static bool overlap_front(struct badblocks *bb, int front,
+			  struct badblocks_context *bad)
+{
+	u64 *p = bb->page;
+
+	if (bad->start >= BB_OFFSET(p[front]) &&
+	    bad->start < BB_END(p[front]))
+		return true;
+	return false;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' is exactly backward
+ * overlapped with the bad range (from bad table) indexed by 'behind'.
+ */
+static bool overlap_behind(struct badblocks *bb, struct badblocks_context *bad,
+			   int behind)
+{
+	u64 *p = bb->page;
+
+	if (bad->start < BB_OFFSET(p[behind]) &&
+	    (bad->start + bad->len) > BB_OFFSET(p[behind]))
+		return true;
+	return false;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' can overwrite the bad
+ * range (from bad table) indexed by 'prev'.
+ *
+ * The range indicated by 'bad' can overwrite the bad range indexed by
+ * 'prev' when,
+ * 1) The whole range indicated by 'bad' can cover partial or whole bad
+ *    range (from bad table) indexed by 'prev'.
+ * 2) The ack value of 'bad' is larger or equal to the ack value of bad
+ *    range 'prev'.
+ *
+ * If the overwriting doesn't cover the whole bad range (from bad table)
+ * indexed by 'prev', new range might be split from existing bad range,
+ * 1) The overwrite covers head or tail part of existing bad range, 1
+ *    extra bad range will be split and added into the bad table.
+ * 2) The overwrite covers middle of existing bad range, 2 extra bad
+ *    ranges will be split (ahead and after the overwritten range) and
+ *    added into the bad table.
+ * The number of extra split ranges of the overwriting is stored in
+ * 'extra' and returned for the caller.
+ */
+static bool can_front_overwrite(struct badblocks *bb, int prev,
+				struct badblocks_context *bad, int *extra)
+{
+	u64 *p = bb->page;
+	int len;
+
+	WARN_ON(!overlap_front(bb, prev, bad));
+
+	if (BB_ACK(p[prev]) >= bad->ack)
+		return false;
+
+	if (BB_END(p[prev]) <= (bad->start + bad->len)) {
+		len = BB_END(p[prev]) - bad->start;
+		if (BB_OFFSET(p[prev]) == bad->start)
+			*extra = 0;
+		else
+			*extra = 1;
+
+		bad->len = len;
+	} else {
+		if (BB_OFFSET(p[prev]) == bad->start)
+			*extra = 1;
+		else
+		/*
+		 * prev range will be split into two, beside the overwritten
+		 * one, an extra slot needed from bad table.
+		 */
+			*extra = 2;
+	}
+
+	if ((bb->count + (*extra)) >= MAX_BADBLOCKS)
+		return false;
+
+	return true;
+}
+
+/*
+ * Do the overwrite from the range indicated by 'bad' to the bad range
+ * (from bad table) indexed by 'prev'.
+ * The previously called can_front_overwrite() will provide how many
+ * extra bad range(s) might be split and added into the bad table. All
+ * the splitting cases in the bad table will be handled here.
+ */
+static int front_overwrite(struct badblocks *bb, int prev,
+			   struct badblocks_context *bad, int extra)
+{
+	u64 *p = bb->page;
+	int n = extra;
+	sector_t orig_end = BB_END(p[prev]);
+	int orig_ack = BB_ACK(p[prev]);
+
+	switch (extra) {
+	case 0:
+		p[prev] = BB_MAKE(BB_OFFSET(p[prev]), BB_LEN(p[prev]),
+				  bad->ack);
+		break;
+	case 1:
+		if (BB_OFFSET(p[prev]) == bad->start) {
+			p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+					  bad->len, bad->ack);
+			memmove(p + prev + 2, p + prev + 1,
+				(bb->count - prev - 1) * 8);
+			p[prev + 1] = BB_MAKE(bad->start + bad->len,
+					      orig_end - BB_END(p[prev]),
+					      orig_ack);
+		} else {
+			p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+					  bad->start - BB_OFFSET(p[prev]),
+					  BB_ACK(p[prev]));
+			memmove(p + prev + 1 + n, p + prev + 1,
+				(bb->count - prev - 1) * 8);
+			p[prev + 1] = BB_MAKE(bad->start, bad->len, bad->ack);
+		}
+		break;
+	case 2:
+		p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+				  bad->start - BB_OFFSET(p[prev]),
+				  BB_ACK(p[prev]));
+		memmove(p + prev + 1 + n, p + prev + 1,
+			(bb->count - prev - 1) * 8);
+		p[prev + 1] = BB_MAKE(bad->start, bad->len, bad->ack);
+		p[prev + 2] = BB_MAKE(BB_END(p[prev + 1]),
+				      orig_end - BB_END(p[prev + 1]),
+				      BB_ACK(p[prev]));
+		break;
+	default:
+		break;
+	}
+
+	return bad->len;
+}
+
+/*
+ * Explicitly insert a range indicated by 'bad' to the bad table, where
+ * the location is indexed by 'at'.
+ */
+static int insert_at(struct badblocks *bb, int at, struct badblocks_context *bad)
+{
+	u64 *p = bb->page;
+	sector_t sectors = bad->len;
+	sector_t s = bad->start;
+	int ack = bad->ack;
+	int len;
+
+	WARN_ON(badblocks_full(bb));
+
+	len = min_t(sector_t, sectors, BB_MAX_LEN);
+	if (at < bb->count)
+		memmove(p + at + 1, p + at, (bb->count - at) * 8);
+	p[at] = BB_MAKE(s, len, ack);
+
+	return len;
+}
+
+static void badblocks_update_acked(struct badblocks *bb)
+{
+	u64 *p = bb->page;
+	int i;
+	bool unacked = false;
+
+	if (!bb->unacked_exist)
+		return;
+
+	for (i = 0; i < bb->count ; i++) {
+		if (!BB_ACK(p[i])) {
+			unacked = true;
+			break;
+		}
+	}
+
+	if (!unacked)
+		bb->unacked_exist = 0;
+}
+
+/* Do exact work to set bad block range into the bad block table */
+static int _badblocks_set(struct badblocks *bb, sector_t s, int sectors,
+			  int acknowledged)
+{
+	u64 *p;
+	struct badblocks_context bad;
+	int prev = -1, hint = -1;
+	int len = 0, added = 0;
+	int retried = 0, space_desired = 0;
+	int rv = 0;
+	unsigned long flags;
+
+	if (bb->shift < 0)
+		/* badblocks are disabled */
+		return 1;
+
+	if (sectors == 0)
+		/* Invalid sectors number */
+		return 1;
+
+	if (bb->shift) {
+		/* round the start down, and the end up */
+		sector_t next = s + sectors;
+
+		rounddown(s, bb->shift);
+		roundup(next, bb->shift);
+		sectors = next - s;
+	}
+
+	write_seqlock_irqsave(&bb->lock, flags);
+
+	bad.orig_start = s;
+	bad.orig_len = sectors;
+	bad.ack = acknowledged;
+	p = bb->page;
+
+re_insert:
+	bad.start = s;
+	bad.len = sectors;
+	len = 0;
+
+	if (badblocks_empty(bb)) {
+		len = insert_at(bb, 0, &bad);
+		bb->count++;
+		added++;
+		goto update_sectors;
+	}
+
+	prev = prev_badblocks(bb, &bad, hint);
+
+	/* start before all badblocks */
+	if (prev < 0) {
+		if (!badblocks_full(bb)) {
+			/* insert on the first */
+			if (bad.len > (BB_OFFSET(p[0]) - bad.start))
+				bad.len = BB_OFFSET(p[0]) - bad.start;
+			len = insert_at(bb, 0, &bad);
+			bb->count++;
+			added++;
+			hint = 0;
+			goto update_sectors;
+		}
+
+		/* No sapce, try to merge */
+		if (overlap_behind(bb, &bad, 0)) {
+			if (can_merge_behind(bb, &bad, 0)) {
+				len = behind_merge(bb, &bad, 0);
+				added++;
+			} else {
+				len = min_t(sector_t,
+					    BB_OFFSET(p[0]) - s, sectors);
+				space_desired = 1;
+			}
+			hint = 0;
+			goto update_sectors;
+		}
+
+		/* no table space and give up */
+		goto out;
+	}
+
+	/* in case p[prev-1] can be merged with p[prev] */
+	if (can_combine_front(bb, prev, &bad)) {
+		front_combine(bb, prev);
+		bb->count--;
+		added++;
+		hint = prev - 1;
+		goto update_sectors;
+	}
+
+	if (overlap_front(bb, prev, &bad)) {
+		if (can_merge_front(bb, prev, &bad)) {
+			len = front_merge(bb, prev, &bad);
+			added++;
+			hint = prev - 1;
+		} else {
+			int extra = 0;
+
+			if (!can_front_overwrite(bb, prev, &bad, &extra)) {
+				len = min_t(sector_t,
+					    BB_END(p[prev]) - s, sectors);
+				hint = prev;
+				goto update_sectors;
+			}
+
+			len = front_overwrite(bb, prev, &bad, extra);
+			added++;
+			bb->count += extra;
+			hint = prev;
+
+			if (prev > 0 && can_combine_front(bb, prev, &bad)) {
+				front_combine(bb, prev);
+				bb->count--;
+				hint = prev - 1;
+			}
+		}
+		goto update_sectors;
+	}
+
+	if (can_merge_front(bb, prev, &bad)) {
+		len = front_merge(bb, prev, &bad);
+		added++;
+		hint = prev;
+		goto update_sectors;
+	}
+
+	/* if no space in table, still try to merge in the covered range */
+	if (badblocks_full(bb)) {
+		/* skip the cannot-merge range */
+		if (((prev + 1) < bb->count) &&
+		    overlap_behind(bb, &bad, prev + 1) &&
+		    ((s + sectors) >= BB_END(p[prev + 1]))) {
+			len = BB_END(p[prev + 1]) - s;
+			hint = prev + 1;
+			goto update_sectors;
+		}
+
+		/* no retry any more */
+		len = sectors;
+		space_desired = 1;
+		hint = -1;
+		goto update_sectors;
+	}
+
+	/* cannot merge and there is space in bad table */
+	if ((prev + 1) < bb->count &&
+	    overlap_behind(bb, &bad, prev + 1))
+		bad.len = min_t(sector_t,
+				bad.len, BB_OFFSET(p[prev + 1]) - bad.start);
+
+	len = insert_at(bb, prev + 1, &bad);
+	bb->count++;
+	added++;
+	hint = prev + 1;
+
+update_sectors:
+	s += len;
+	sectors -= len;
+
+	if (sectors > 0)
+		goto re_insert;
+
+	WARN_ON(sectors < 0);
+
+	/* Check whether the following already set range can be merged */
+	if ((prev + 1) < bb->count &&
+	    BB_END(p[prev]) == BB_OFFSET(p[prev + 1]) &&
+	    (BB_LEN(p[prev]) + BB_LEN(p[prev + 1])) <= BB_MAX_LEN &&
+	    BB_ACK(p[prev]) == BB_ACK(p[prev + 1])) {
+		p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+				  BB_LEN(p[prev]) + BB_LEN(p[prev + 1]),
+				  BB_ACK(p[prev]));
+
+		if ((prev + 2) < bb->count)
+			memmove(p + prev + 1, p + prev + 2,
+				(bb->count -  (prev + 2)) * 8);
+		bb->count--;
+	}
+
+	if (space_desired && !badblocks_full(bb)) {
+		s = bad.orig_start;
+		sectors = bad.orig_len;
+		space_desired = 0;
+		if (retried++ < 3)
+			goto re_insert;
+	}
+
+out:
+	if (added) {
+		set_changed(bb);
+
+		if (!acknowledged)
+			bb->unacked_exist = 1;
+		else
+			badblocks_update_acked(bb);
+	}
+
+	write_sequnlock_irqrestore(&bb->lock, flags);
+
+	if (!added)
+		rv = 1;
+
+	return rv;
+}
+
+/*
+ * Clear the bad block range from bad block table which is front overlapped
+ * with the clearing range. The return value is how many sectors from an
+ * already set bad block range are cleared. If the whole bad block range is
+ * covered by the clearing range and fully cleared, 'delete' is set as 1 for
+ * the caller to reduce bb->count.
+ */
+static int front_clear(struct badblocks *bb, int prev,
+		       struct badblocks_context *bad, int *deleted)
+{
+	sector_t sectors = bad->len;
+	sector_t s = bad->start;
+	u64 *p = bb->page;
+	int cleared = 0;
+
+	*deleted = 0;
+	if (s == BB_OFFSET(p[prev])) {
+		if (BB_LEN(p[prev]) > sectors) {
+			p[prev] = BB_MAKE(BB_OFFSET(p[prev]) + sectors,
+					  BB_LEN(p[prev]) - sectors,
+					  BB_ACK(p[prev]));
+			cleared = sectors;
+		} else {
+			/* BB_LEN(p[prev]) <= sectors */
+			cleared = BB_LEN(p[prev]);
+			if ((prev + 1) < bb->count)
+				memmove(p + prev, p + prev + 1,
+				       (bb->count - prev - 1) * 8);
+			*deleted = 1;
+		}
+	} else if (s > BB_OFFSET(p[prev])) {
+		if (BB_END(p[prev]) <= (s + sectors)) {
+			cleared = BB_END(p[prev]) - s;
+			p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+					  s - BB_OFFSET(p[prev]),
+					  BB_ACK(p[prev]));
+		} else {
+			/* Splitting is handled in front_splitting_clear() */
+			BUG();
+		}
+	}
+
+	return cleared;
+}
+
+/*
+ * Handle the condition that the clearing range hits middle of an already set
+ * bad block range from bad block table. In this condition the existing bad
+ * block range is split into two after the middle part is cleared.
+ */
+static int front_splitting_clear(struct badblocks *bb, int prev,
+				  struct badblocks_context *bad)
+{
+	sector_t sectors = bad->len;
+	sector_t s = bad->start;
+	u64 *p = bb->page;
+	u64 end = BB_END(p[prev]);
+	int ack = BB_ACK(p[prev]);
+
+	p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+			  s - BB_OFFSET(p[prev]),
+			  ack);
+	memmove(p + prev + 2, p + prev + 1, (bb->count - prev - 1) * 8);
+	p[prev + 1] = BB_MAKE(s + sectors, end - s - sectors, ack);
+	return sectors;
+}
+
+/* Do the exact work to clear bad block range from the bad block table */
+static int _badblocks_clear(struct badblocks *bb, sector_t s, int sectors)
+{
+	u64 *p;
+	struct badblocks_context bad;
+	int prev = -1, hint = -1;
+	int len = 0, cleared = 0;
+	int rv = 0;
+
+	if (bb->shift < 0)
+		/* badblocks are disabled */
+		return 1;
+
+	if (sectors == 0)
+		/* Invalid sectors number */
+		return 1;
+
+	if (bb->shift) {
+		sector_t target;
+
+		/* When clearing we round the start up and the end down.
+		 * This should not matter as the shift should align with
+		 * the block size and no rounding should ever be needed.
+		 * However it is better the think a block is bad when it
+		 * isn't than to think a block is not bad when it is.
+		 */
+		target = s + sectors;
+		roundup(s, bb->shift);
+		rounddown(target, bb->shift);
+		sectors = target - s;
+	}
+
+	write_seqlock_irq(&bb->lock);
+
+	bad.orig_start = s;
+	bad.orig_len = sectors;
+	bad.ack = true;
+	p = bb->page;
+
+re_clear:
+	bad.start = s;
+	bad.len = sectors;
+
+	if (badblocks_empty(bb)) {
+		len = sectors;
+		cleared++;
+		goto update_sectors;
+	}
+
+
+	prev = prev_badblocks(bb, &bad, hint);
+
+	/* Start before all badblocks */
+	if (prev < 0) {
+		if (overlap_behind(bb, &bad, 0)) {
+			len = BB_OFFSET(p[0]) - s;
+			hint = prev;
+		} else {
+			len = sectors;
+		}
+		/*
+		 * Both situations are to clear non-bad range,
+		 * should be treated as successful
+		 */
+		cleared++;
+		goto update_sectors;
+	}
+
+	/* Start after all badblocks */
+	if ((prev + 1) >= bb->count && !overlap_front(bb, prev, &bad)) {
+		len = sectors;
+		cleared++;
+		goto update_sectors;
+	}
+
+	/* Clear will split a bad record but the table is full */
+	if (badblocks_full(bb) && (BB_OFFSET(p[prev]) < bad.start) &&
+	    (BB_END(p[prev]) > (bad.start + sectors))) {
+		len = sectors;
+		printf("Warn: no space to split for clear\n");
+		goto update_sectors;
+	}
+
+	if (overlap_front(bb, prev, &bad)) {
+		if ((BB_OFFSET(p[prev]) < bad.start) &&
+		    (BB_END(p[prev]) > (bad.start + bad.len))) {
+			/* Splitting */
+			if ((bb->count + 1) < MAX_BADBLOCKS) {
+				len = front_splitting_clear(bb, prev, &bad);
+				bb->count += 1;
+				cleared++;
+			} else {
+				/* No space to split, give up */
+				printf("Warn: no space to split for clear\n");
+				len = sectors;
+			}
+		} else {
+			int deleted = 0;
+
+			len = front_clear(bb, prev, &bad, &deleted);
+			bb->count -= deleted;
+			cleared++;
+			hint = prev;
+		}
+
+		goto update_sectors;
+	}
+
+	/* Not front overlap, but behind overlap */
+	if ((prev + 1) < bb->count && overlap_behind(bb, &bad, prev + 1)) {
+		len = BB_OFFSET(p[prev + 1]) - bad.start;
+		hint = prev + 1;
+		/* Clear non-bad range should be treated as successful */
+		cleared++;
+		goto update_sectors;
+	}
+
+	/* Not cover any badblocks range in the table */
+	len = sectors;
+	/* Clear non-bad range should be treated as successful */
+	cleared++;
+
+update_sectors:
+	s += len;
+	sectors -= len;
+
+	if (sectors > 0)
+		goto re_clear;
+
+	WARN_ON(sectors < 0);
+
+	if (cleared) {
+		badblocks_update_acked(bb);
+		set_changed(bb);
+	}
+
+	write_sequnlock_irq(&bb->lock);
+
+	if (!cleared)
+		rv = 1;
+
+	return rv;
+}
+
+/* Do the exact work to check bad blocks range from the bad block table */
+static int _badblocks_check(struct badblocks *bb, sector_t s, int sectors,
+			    sector_t *first_bad, int *bad_sectors)
+{
+	u64 *p;
+	struct badblocks_context bad;
+	int prev = -1, hint = -1, set = 0;
+	int unacked_badblocks, acked_badblocks;
+	int len, rv;
+	unsigned int seq;
+
+	WARN_ON(bb->shift < 0 || sectors == 0);
+
+	if (bb->shift > 0) {
+		sector_t target;
+
+		/* round the start down, and the end up */
+		target = s + sectors;
+		rounddown(s, bb->shift);
+		roundup(target, bb->shift);
+		sectors = target - s;
+	}
+
+retry:
+	seq = read_seqbegin(&bb->lock);
+
+	bad.orig_start = s;
+	bad.orig_len = sectors;
+	p = bb->page;
+	unacked_badblocks = 0;
+	acked_badblocks = 0;
+
+re_check:
+	bad.start = s;
+	bad.len = sectors;
+
+	if (badblocks_empty(bb)) {
+		len = sectors;
+		goto update_sectors;
+	}
+
+	prev = prev_badblocks(bb, &bad, hint);
+
+	/* start after all badblocks */
+	if ((prev + 1) >= bb->count && !overlap_front(bb, prev, &bad)) {
+		len = sectors;
+		goto update_sectors;
+	}
+
+	if (overlap_front(bb, prev, &bad)) {
+		if (BB_ACK(p[prev]))
+			acked_badblocks++;
+		else
+			unacked_badblocks++;
+
+		if (BB_END(p[prev]) >= (s + sectors))
+			len = sectors;
+		else
+			len = BB_END(p[prev]) - s;
+
+		if (set == 0) {
+			*first_bad = BB_OFFSET(p[prev]);
+			*bad_sectors = BB_LEN(p[prev]);
+			set = 1;
+		}
+		goto update_sectors;
+	}
+
+	/* Not front overlap, but behind overlap */
+	if ((prev + 1) < bb->count && overlap_behind(bb, &bad, prev + 1)) {
+		len = BB_OFFSET(p[prev + 1]) - bad.start;
+		hint = prev + 1;
+		goto update_sectors;
+	}
+
+	/* not cover any badblocks range in the table */
+	len = sectors;
+
+update_sectors:
+	s += len;
+	sectors -= len;
+
+	if (sectors > 0)
+		goto re_check;
+
+	WARN_ON(sectors < 0);
+
+	if (unacked_badblocks > 0)
+		rv = -1;
+	else if (acked_badblocks > 0)
+		rv = 1;
+	else
+		rv = 0;
+
+	if (read_seqretry(&bb->lock, seq))
+		goto retry;
+
+	return rv;
+}
+
+/**
+ * badblocks_check() - check a given range for bad sectors
+ * @bb:		the badblocks structure that holds all badblock information
+ * @s:		sector (start) at which to check for badblocks
+ * @sectors:	number of sectors to check for badblocks
+ * @first_bad:	pointer to store location of the first badblock
+ * @bad_sectors: pointer to store number of badblocks after @first_bad
+ *
+ * We can record which blocks on each device are 'bad' and so just
+ * fail those blocks, or that stripe, rather than the whole device.
+ * Entries in the bad-block table are 64bits wide.  This comprises:
+ * Length of bad-range, in sectors: 0-511 for lengths 1-512
+ * Start of bad-range, sector offset, 54 bits (allows 8 exbibytes)
+ *  A 'shift' can be set so that larger blocks are tracked and
+ *  consequently larger devices can be covered.
+ * 'Acknowledged' flag - 1 bit. - the most significant bit.
+ *
+ * Locking of the bad-block table uses a seqlock so badblocks_check
+ * might need to retry if it is very unlucky.
+ * We will sometimes want to check for bad blocks in a bi_end_io function,
+ * so we use the write_seqlock_irq variant.
+ *
+ * When looking for a bad block we specify a range and want to
+ * know if any block in the range is bad.  So we binary-search
+ * to the last range that starts at-or-before the given endpoint,
+ * (or "before the sector after the target range")
+ * then see if it ends after the given start.
+ *
+ * Return:
+ *  0: there are no known bad blocks in the range
+ *  1: there are known bad block which are all acknowledged
+ * -1: there are bad blocks which have not yet been acknowledged in metadata.
+ * plus the start/length of the first bad section we overlap.
+ */
+int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
+			sector_t *first_bad, int *bad_sectors)
+{
+	return _badblocks_check(bb, s, sectors, first_bad, bad_sectors);
+}
+EXPORT_SYMBOL_GPL(badblocks_check);
+
+/**
+ * badblocks_set() - Add a range of bad blocks to the table.
+ * @bb:		the badblocks structure that holds all badblock information
+ * @s:		first sector to mark as bad
+ * @sectors:	number of sectors to mark as bad
+ * @acknowledged: weather to mark the bad sectors as acknowledged
+ *
+ * This might extend the table, or might contract it if two adjacent ranges
+ * can be merged. We binary-search to find the 'insertion' point, then
+ * decide how best to handle it.
+ *
+ * Return:
+ *  0: success
+ *  1: failed to set badblocks (out of space)
+ */
+int badblocks_set(struct badblocks *bb, sector_t s, int sectors,
+			int acknowledged)
+{
+	return _badblocks_set(bb, s, sectors, acknowledged);
+}
+EXPORT_SYMBOL_GPL(badblocks_set);
+
+/**
+ * badblocks_clear() - Remove a range of bad blocks to the table.
+ * @bb:		the badblocks structure that holds all badblock information
+ * @s:		first sector to mark as bad
+ * @sectors:	number of sectors to mark as bad
+ *
+ * This may involve extending the table if we spilt a region,
+ * but it must not fail.  So if the table becomes full, we just
+ * drop the remove request.
+ *
+ * Return:
+ *  0: success
+ *  1: failed to clear badblocks
+ */
+int badblocks_clear(struct badblocks *bb, sector_t s, int sectors)
+{
+	return _badblocks_clear(bb, s, sectors);
+}
+EXPORT_SYMBOL_GPL(badblocks_clear);
+
+/**
+ * ack_all_badblocks() - Acknowledge all bad blocks in a list.
+ * @bb:		the badblocks structure that holds all badblock information
+ *
+ * This only succeeds if ->changed is clear.  It is used by
+ * in-kernel metadata updates
+ */
+void ack_all_badblocks(struct badblocks *bb)
+{
+	if (bb->page == NULL || bb->changed)
+		/* no point even trying */
+		return;
+	write_seqlock_irq(&bb->lock);
+
+	if (bb->changed == 0 && bb->unacked_exist) {
+		u64 *p = bb->page;
+		int i;
+
+		for (i = 0; i < bb->count ; i++) {
+			if (!BB_ACK(p[i])) {
+				sector_t start = BB_OFFSET(p[i]);
+				int len = BB_LEN(p[i]);
+
+				p[i] = BB_MAKE(start, len, 1);
+			}
+		}
+		bb->unacked_exist = 0;
+	}
+	write_sequnlock_irq(&bb->lock);
+}
+EXPORT_SYMBOL_GPL(ack_all_badblocks);
+
+/**
+ * badblocks_show() - sysfs access to bad-blocks list
+ * @bb:		the badblocks structure that holds all badblock information
+ * @page:	buffer received from sysfs
+ * @unack:	weather to show unacknowledged badblocks
+ *
+ * Return:
+ *  Length of returned data
+ */
+ssize_t badblocks_show(struct badblocks *bb, int unack)
+{
+	size_t len;
+	int i;
+	u64 *p = bb->page;
+	char *_page;
+	int size = 64*4096;
+	unsigned int seq;
+
+	if (bb->shift < 0)
+		return 0;
+
+	_page = malloc(size);
+	if (!_page) {
+		printf("alloc _page failed\n");
+		return 0;
+	}
+	memset(_page, 0, size);
+retry:
+	seq = read_seqbegin(&bb->lock);
+
+	len = 0;
+	i = 0;
+
+	while (len < size && i < bb->count) {
+		sector_t s = BB_OFFSET(p[i]);
+		unsigned int length = BB_LEN(p[i]);
+		int ack = BB_ACK(p[i]);
+
+		i++;
+
+		if (unack && ack)
+			continue;
+
+		len += snprintf(_page+len, size - len, "%llu %u\n",
+				(unsigned long long)s << bb->shift,
+				length << bb->shift);
+	}
+	if (unack && len == 0)
+		bb->unacked_exist = 0;
+
+	printf("%s\n", _page);
+	free(_page);
+
+	if (read_seqretry(&bb->lock, seq))
+		goto retry;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(badblocks_show);
+
+/**
+ * badblocks_store() - sysfs access to bad-blocks list
+ * @bb:		the badblocks structure that holds all badblock information
+ * @page:	buffer received from sysfs
+ * @len:	length of data received from sysfs
+ * @unack:	weather to show unacknowledged badblocks
+ *
+ * Return:
+ *  Length of the buffer processed or -ve error.
+ */
+ssize_t badblocks_store(struct badblocks *bb, const char *page, size_t len,
+			int unack)
+{
+	unsigned long long sector;
+	int length;
+	char newline;
+
+	switch (sscanf(page, "%llu %d%c", &sector, &length, &newline)) {
+	case 3:
+		if (newline != '\n')
+			return -EINVAL;
+		fallthrough;
+	case 2:
+		if (length <= 0)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (badblocks_set(bb, sector, length, !unack))
+		return -ENOSPC;
+	else
+		return len;
+}
+EXPORT_SYMBOL_GPL(badblocks_store);
+
+static int __badblocks_init(struct device *dev, struct badblocks *bb,
+		int enable)
+{
+	bb->dev = dev;
+	bb->count = 0;
+	if (enable)
+		bb->shift = 0;
+	else
+		bb->shift = -1;
+	if (dev)
+		bb->page = devm_kzalloc(dev, PAGE_SIZE, GFP_KERNEL);
+	else
+		bb->page = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!bb->page) {
+		bb->shift = -1;
+		return -ENOMEM;
+	}
+	seqlock_init(&bb->lock);
+
+	return 0;
+}
+
+/**
+ * badblocks_init() - initialize the badblocks structure
+ * @bb:		the badblocks structure that holds all badblock information
+ * @enable:	weather to enable badblocks accounting
+ *
+ * Return:
+ *  0: success
+ *  -ve errno: on error
+ */
+int badblocks_init(struct badblocks *bb, int enable)
+{
+	return __badblocks_init(NULL, bb, enable);
+}
+EXPORT_SYMBOL_GPL(badblocks_init);
+
+int devm_init_badblocks(struct device *dev, struct badblocks *bb)
+{
+	if (!bb)
+		return -EINVAL;
+	return __badblocks_init(dev, bb, 1);
+}
+EXPORT_SYMBOL_GPL(devm_init_badblocks);
+
+/**
+ * badblocks_exit() - free the badblocks structure
+ * @bb:		the badblocks structure that holds all badblock information
+ */
+void badblocks_exit(struct badblocks *bb)
+{
+	if (!bb)
+		return;
+	if (bb->dev)
+		devm_kfree(bb->dev, bb->page);
+	else
+		kfree(bb->page);
+	bb->page = NULL;
+}
+EXPORT_SYMBOL_GPL(badblocks_exit);
+
+
+/*
+ * Test case related
+ */
+char good_sector[512];
+char bad_unack_sector[512];
+char bad_acked_sector[512];
+
+#define BB_SET	0
+#define BB_CLN	1
+
+unsigned int rand_seed = 2;
+
+char bb_ops[] = {0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1};
+char bb_ack[] = {1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 0};
+
+/* disk file length is 256MB */
+#define DISKFILE_SECTORS	((256 << 20) >> 9)
+#define MAX_SET_SIZE		(DISKFILE_SECTORS/256)
+#define MAX_CLN_SIZE		(DISKFILE_SECTORS/1024)
+
+#define BUF_LEN	(8<<10)
+
+void write_badblocks_log(struct badblocks *bb, char *dir, unsigned long seq,
+			 sector_t bb_start, sector_t bb_len,
+			 int ops, int ack)
+{
+	char path[512];
+	char buf[8192];
+	u64 *p = bb->page;
+	int len, size, i;
+	int fd;
+
+
+	size = sizeof(buf);
+	memset(buf, 0, sizeof(buf));
+	len = 0;
+
+	len += snprintf(buf + len, size - len, "============ %lu ============\n\n", seq);
+	if (ops == BB_SET)
+		len += snprintf(buf + len, size - len, "set: start %llu, len %llu, ack %d\n",
+				bb_start, bb_len, ack);
+	else
+		len += snprintf(buf + len, size - len, "clear: start %llu, len %llu\n",
+				bb_start, bb_len);
+
+	len += snprintf(buf + len, size - len, "=============================\n\n");
+
+	i = 0;
+	while (len < size && i < bb->count) {
+		sector_t s = BB_OFFSET(p[i]);
+		unsigned int length = BB_LEN(p[i]);
+		int ack = BB_ACK(p[i]);
+
+		i++;
+
+		len += snprintf(buf + len, size - len, "%llu %u [%u]\n",
+				(unsigned long long)s << bb->shift,
+				length << bb->shift,
+				ack);
+	}
+
+	snprintf(path, 512, "%s/seq-%.8lu", dir ? dir : ".", seq);
+	unlink(path);
+	fd = open(path, O_CREAT|O_RDWR, 0644);
+	if (fd < 0) {
+		printf("fail to create file %s\n", path);
+		return;
+	}
+	write(fd, buf, len);
+	fsync(fd);
+	close(fd);
+}
+
+
+int verify_bad_sectors(sector_t start, sector_t len, int expected, int fd)
+{
+	int ret = 0;
+	char buf[BUF_LEN];
+	unsigned long offset = start << 9;
+	unsigned long unread = len << 9;
+
+	if ((start + len) > DISKFILE_SECTORS)
+		printf("Error: invalid verify range: s %llu, l %llu\n, limit %u\n",
+		       start, len, DISKFILE_SECTORS);
+
+	while (unread > 0) {
+		unsigned long read_bytes = min(unread, BUF_LEN);
+		unsigned long i;
+		ssize_t _ret;
+
+		memset(buf, 0, sizeof(buf));
+		_ret = pread(fd, buf, read_bytes, offset);
+		if (_ret != read_bytes) {
+			printf("Error: to read %lu bytes, return %lu bytes\n",
+			       read_bytes, _ret);
+		}
+
+		for (i = 0; i < read_bytes; i++) {
+			if (buf[i] != expected) {
+				printf("Unexpected sector value %u (should be %u) at sector %lu"
+				       " offset byte %lu\n",
+				       buf[i], expected, (offset+i) >> 9,
+				       (offset + i) % 512);
+				exit(1);
+				if (ret == 0)
+					ret = -EIO;
+			}
+		}
+
+		if (ret)
+			goto out;
+
+		unread -= read_bytes;
+		offset += read_bytes;
+	}
+
+out:
+	return ret;
+}
+
+int verify_badblocks_file(struct badblocks *bb, int fd, unsigned long seq)
+{
+	int ret = 0;
+	sector_t size = DISKFILE_SECTORS;
+	u64 *p = bb->page;
+	int i = 0;
+	unsigned long prev_pos, pos;
+
+	prev_pos = pos = 0;
+	while ((size > 0) && (i < bb->count)) {
+		sector_t s = BB_OFFSET(p[i]);
+		unsigned int length = BB_LEN(p[i]);
+		int ack = BB_ACK(p[i]);
+
+		pos = s;
+
+		/* verify non-bad area */
+		if (pos > prev_pos) {
+			ret = verify_bad_sectors(prev_pos, pos - prev_pos, 0, fd);
+			if (ret < 0) {
+				printf("%s:%d fail to verify good sectors [%lu, %lu), error: %s\n",
+				      __func__, __LINE__, prev_pos, pos, strerror(-ret));
+				goto out;
+			}
+
+			size -= (pos - prev_pos);
+		}
+
+		/* verify bad area */
+		ret = verify_bad_sectors(pos, length, ack ? 2 : 1, fd);
+		if (ret < 0) {
+			printf("%s:%d fail to verify bad sectors [%lu, %u) ack %d, error: %s\n",
+			       __func__, __LINE__, pos, length, ack, strerror(ret));
+			goto out;
+		}
+
+		size -= length;
+		i++;
+		prev_pos = pos + length;
+	}
+
+	if (i < bb->count) {
+		printf("Error: total %d bad records, verified %d, left %d\n",
+		       bb->count, i, bb->count - i);
+		if (size)
+			printf("Error: still have %llu sectors not verified\n",
+			       size);
+		ret = -EIO;
+		goto out;
+	}
+
+	/* verify rested non-bad area */
+	if (size) {
+		pos = DISKFILE_SECTORS;
+		ret = verify_bad_sectors(prev_pos, pos - prev_pos, 0, fd);
+		if (ret < 0) {
+			printf("%s:%d fail to verify good sectors [%lu, %lu), error: %s\n",
+			      __func__, __LINE__, prev_pos, pos, strerror(-ret));
+			goto out;
+		}
+	}
+
+	printf("verify badblocks file successfully (seq %lu)\n", seq);
+out:
+	return ret;
+}
+
+
+int _write_diskfile(int fd, int ops,
+		    sector_t start, sector_t len, int ack)
+{
+	off_t pos = start << 9;
+	char sector[512];
+
+	if ((start + len) > DISKFILE_SECTORS)
+		len = DISKFILE_SECTORS - start;
+
+	if (len == 0) {
+		printf("Error: write diskfile zero-length at %llu len %llu\n",
+		       start, len);
+		return -EINVAL;
+	}
+
+	if (ops == BB_CLN) {
+		while (len > 0) {
+			pwrite(fd, good_sector, 512, pos);
+			pos += 512;
+			len--;
+		}
+		fsync(fd);
+		return 0;
+	}
+
+	/* badblocks set */
+	while (len > 0) {
+		pread(fd, sector, 512, pos);
+		if (!memcmp(sector, good_sector, 512)) {
+			if (ack)
+				pwrite(fd, bad_acked_sector, 512, pos);
+			else
+				pwrite(fd, bad_unack_sector, 512, pos);
+
+//			printf("write %d at sector %lu\n", ack ? 2 : 1, pos >> 9);
+		} else if (!memcmp(sector, bad_unack_sector, 512)) {
+			if (ack) {
+				pwrite(fd, bad_acked_sector, 512, pos);
+//				printf("overwrite 2 at unack sector %lu\n", pos >> 9);
+			} else {
+//				printf("avoid overwrite already unacked sector %lu\n", pos >> 9);
+			}
+		} else if (!memcmp(sector, bad_acked_sector, 512)) {
+//			if (ack)
+//				printf("avoid overwrite already acked sector %lu\n", pos >> 9);
+//			else
+//				printf("cannot overwrite acked sector %lu\n", pos >> 9);
+		} else {
+			printf("Error: unexpected sector at %lu\n", pos >> 9);
+		}
+
+		pos += 512;
+		len--;
+	}
+
+	fsync(fd);
+	return 0;
+}
+
+sector_t fix_writing_length(struct badblocks *bb, int ops, sector_t bb_start,
+			    sector_t bb_len, int ack)
+{
+	sector_t orig_len = bb_len;
+	sector_t ret_len = 0;
+	int prev;
+	struct badblocks_context bad;
+	u64 *p = bb->page;
+
+	bad.orig_start = bb_start;
+	bad.orig_len = bb_len;
+	bad.start = bb_start;
+	bad.len = bb_len;
+	bad.ack = ack;
+
+
+	if (ops == BB_SET) {
+		prev = prev_badblocks(bb, &bad, -1);
+		if (prev < 0) {
+			printf("Unexpected: the set range is not in badblocks table\n");
+			exit(1);
+		}
+
+		if (BB_OFFSET(p[prev]) > bb_start ||
+		    BB_END(p[prev]) <= bb_start ||
+		    BB_ACK(p[prev]) != ack) {
+			printf("Unexpected: fixing range is not in badblocks table\n");
+			exit(1);
+		}
+
+		while (bb_len > 0) {
+			int seg;
+
+			if (BB_END(p[prev]) >= (bb_start + bb_len))
+				seg = bb_len;
+			else
+				seg = BB_END(p[prev]) - bb_start;
+
+			ret_len += seg;
+			bb_start += seg;
+			bb_len -= seg;
+
+			if (bb_len == 0)
+				break;
+
+			if ((prev + 1) >= bb->count ||
+			    BB_END(p[prev]) != BB_OFFSET(p[prev + 1]) ||
+			    BB_ACK(p[prev]) != BB_ACK(p[prev + 1]))
+				break;
+			prev++;
+		}
+	} else if (ops == BB_CLN) {
+		ret_len = bb_len;
+
+	}
+
+	printf("Fix writing bb_len from %llu to %llu\n", orig_len, ret_len);
+	return ret_len;
+}
+
+int write_badblocks_file(struct badblocks *bb, unsigned long seq, int fd)
+{
+	int ret;
+	sector_t bb_start, bb_len;
+	int ops, random;
+
+retry:
+	random = rand_r(&rand_seed);
+	ops = bb_ops[random % sizeof(bb_ops)];
+	random = rand_r(&rand_seed);
+	if (ops == BB_SET)
+		bb_len = random % MAX_SET_SIZE;
+	else
+		bb_len = random % MAX_CLN_SIZE;
+	random = rand_r(&rand_seed);
+	bb_start = random % DISKFILE_SECTORS;
+	if ((bb_start + bb_len) > DISKFILE_SECTORS)
+		bb_len = DISKFILE_SECTORS - bb_start;
+	if (bb_len == 0) {
+		printf("random bb_len is 0, re-generate\n");
+		goto retry;
+	}
+
+
+	if (ops == BB_SET) {
+		int ack;
+
+		random = rand_r(&rand_seed);
+		ack = bb_ack[random % sizeof(bb_ack)];
+
+		bb->changed = 0;
+		ret = badblocks_set(bb, bb_start, bb_len, ack);
+		write_badblocks_log(bb, NULL, seq, bb_start, bb_len, BB_SET, ack);
+		if (ret > 0) {
+			printf("NOTICE: no space or cannot overwwrite badblocks"
+			       "        for badblocks_set(s: %llu, l: %llu, a: %d).\n"
+			       "        Manual check might be necessary if\n"
+			       "        following verification failed.\n",
+			       bb_start, bb_len, ack);
+			return 1;
+		}
+
+		if (badblocks_full(bb) && bb->changed)
+			bb_len = fix_writing_length(bb, ops, bb_start, bb_len, ack);
+		ret = _write_diskfile(fd, ops, bb_start, bb_len, ack);
+	} else {
+		bb->changed = 0;
+		ret = badblocks_clear(bb, bb_start, bb_len);
+		write_badblocks_log(bb, NULL, seq, bb_start, bb_len, BB_CLN, -1);
+		if (ret > 0) {
+			printf("NOTICE: no space for badblocks_clear(s: %llu, l: %llu)\n"
+			       "        Manual check might be necessary if\n"
+			       "        following verification failed.\n",
+			       bb_start, bb_len);
+			return 1;
+		}
+
+		ret = _write_diskfile(fd, ops, bb_start, bb_len, -1);
+	}
+
+	return ret;
+}
+
+#define MAX_BB_TEST_TRIES	(1<<20)
+int do_test(struct badblocks *bb)
+{
+	int ret = 0;
+	unsigned long seq;
+	char diskfile_name[] = "./dummy_disk_file";
+	int diskfile_fd = -1;
+
+	srand(rand_seed);
+
+	unlink(diskfile_name);
+	diskfile_fd = open(diskfile_name, O_CREAT|O_RDWR, 0644);
+	if (diskfile_fd < 0) {
+		printf("fail to create %s, error %s\n",
+		       diskfile_name, strerror(errno));
+		goto out;
+	}
+	ret = fallocate(diskfile_fd, FALLOC_FL_ZERO_RANGE, 0, DISKFILE_SECTORS << 9);
+	if (ret < 0) {
+		printf("fail to allocate zero-filled file, error %s\n",
+		       strerror(errno));
+		goto out;
+	}
+
+	for (seq = 1; seq <= MAX_BB_TEST_TRIES; seq++) {
+		ret = write_badblocks_file(bb, seq, diskfile_fd);
+		if (ret < 0) {
+			printf("fail to generate bad blocks for seq %lu, error %s\n",
+			       seq, strerror(-ret));
+			goto out;
+		}
+		ret = verify_badblocks_file(bb, diskfile_fd, seq);
+		if (ret < 0) {
+			printf("fail to verify bad blocks for seq %lu, error %s\n",
+			       seq, strerror(-ret));
+		}
+	}
+
+out:
+	if (diskfile_fd >= 0)
+		close(diskfile_fd);
+	return ret;
+}
+
+int main(int argc, char *argv[])
+{
+	struct badblocks bblocks;
+	struct badblocks *bb = &bblocks;
+	int i;
+
+	for (i = 0; i < 512; i++) {
+		good_sector[i] = 0;
+		bad_unack_sector[i] = 1;
+		bad_acked_sector[i] = 2;
+	}
+
+	memset(bb, 0, sizeof(struct badblocks));
+	badblocks_init(bb, 1);
+
+	do_test(bb);
+
+	badblocks_exit(bb);
+	return 0;
+}
